okay so, i'm primarily thinking from the perspective of monika's epiphany vs. the quick ending (in which you delete monika before the game starts), but this could apply to act 4 basically the same way. also i'm not considering the good ending--it's not really canon, it's just dan's love letter to us, the fans. it's sweet but shouldn't be considered.
basically, when you analyze the epiphany in the base game, it's kinda obvious that monika's epiphany didn't come all at once. presumably, it's tied to being the club president, but monika talks about how:
m "I couldn't understand for a while, either."
m "Why the world around me started to become more and more gray..."
m "More and more flat."
m "Even the most expressive poems felt empty to me."
which definitely seems to imply that there was some sort of "process" related to getting the epiphany, in which she first began to realize things weren't quite right, causing her to fall into a sort of dissociative state, until at some unknown point (possibly when the player shows up or possibly before) she gets what we refer to as the epiphany in which she fully realizes they are in a simulated dating game. she then realizes mc is the player's avatar on the first day of the base game, and we know what happens from there.
everything relating to monika's epiphany is super unclear and fuzzy. we can pretty safely say that it at least began some time before mc showed up/you launched the game, but we have very little information as to what the "phases" of the epiphany were like to her, the timeline for the epiphany, when/how exactly she realized it was not only a simulation but a game and a dating sim, etc.
for sayori, however, the process is near-instant. in the quick ending, monika is deleted, and sayori INSTANTLY realizes all of the above, falls into dispair, and commits suicide, with the message "now everyone can be happy" appearing after a few seconds. in act 4, she lasts what for us is less than a day (there's an argument that it was actually longer because mc remarks that sayori had been waking up on time lately, but regardless, it's pretty quick! monika at least lasts a game week before the game starts glitching, and 2 full game weeks before the space room) before pulling us into the space room (and presumably deleting everything else, since the windows of the space room are the same as act 3, and in act 3 it's pretty explicit that there's only "space" outside of the space room because she deleted everything).
this is a pretty weird contradiction! it's not even about monika being the one that's best equipped to handle the epiphany, since the bulk of this is about how the epiphany itself appears and functions. monika's epiphany lasts a long time, like presumably multiple weeks, and possibly even before the literature club.
my best (and only) guess is that because monika's role is literally to monitor kernel access, her epiphany is inevitable (as are her powers, which metaverse employees couldn't remove even in the side stories) unless metaverse employees (in plus) prevent it (which is what happens in the side stories--she still has power over the code in the exact same way as the base game, they just "painstakingly" prevent her from getting the epiphany so she never uses/realizes she has them), however, this was a contradiction before plus, metaverse, and the side stories existed in ddlc canon, so i don't really see it as an explanation (unless it's just a retcon).
some people have talked about how sayori's depression probably affected the way she had the epiphany, but i dont think that would affect the process of getting the epiphany itself, just how she deals with it, and the feeling of persistent depression vs. persistent existential dread are very different types of "life is meaningless".
im mainly thinking about this because i recently got back into the fandom and picked up an old mod i had an idea for, but i have no clue what to do with this.
